The thermal conductivity λ, electrical resistivity ρ, and absolute Seebeck coefficient S of two grades of nearly isotropic graphite were measured from 300 to 1000°K both before and after neutron irradiation up to 5.0 × 1021 n/cm2 (>50 keV). Nominal irradiation temperatures were 823, 923, and 1023°K. The thermal resistance, λ−1, of the unirradiated graphites was proportional to T from 500 to 1000°K. Neutron irradiation decreased λ at 300°K by a factor of 4.5 and increased ρ at 300°K by 2.5, in general agreement with previous investigations, and irradiation changed S from small negative values to large positive ones. The product of thermal conductivity and electrical resistivity was nearly constant with fluence from 2.6 × 1021 to 5.0 × 1021 n/cm2.